The heart beats throughout life and this beating may vary in rate but is usually rhythmical. However, there are conditions where this rhythm is affected. The heartbeat becomes irregular and may also become abnormally rapid (above 100 beats per minute). This irregularity is known as an arrhythmia and one such type is atrial fibrillation.
What is atrial fibrillation?
Atrial fibrillation is where the upper chambers of the heart beat uncontrollably. This quivering or fluttering of the heart can cause problems with blood circulation through the heart. Atrial fibrillation is the most common type of arrhythmia (irregular heartbeat). It can increase the risk of blood clot formation in the heart which may lead to a stroke or can even result in heart failure if persistent.
Atrial fibrillation is more likely to arise with heart disease or damage. However, it can sometimes occur when there is no problem with the heart. Atrial fibrillation will affect at least 1 in 4 American adults aged 40 years and older during their lifetime. It is more common in older adults and affects men more frequently than women.
Read more on fluttering heart.
Causes of Atrial Fibrillation
The atria (singular ~ atrium) are the two smaller chambers that lie in the upper part of the heart. It receives blood which is then passed on to the ventricles. From here the ventricles pump the blood out of the heart. The atria contract first while the ventricles relax to receive the blood. Then ventricles contract to push out this blood to the rest of the body.
The right atrium receives deoxygenated (low oxygen) which is passed to the right ventricle. From here the right ventricle sends the blood to the lungs where it is oxygenated. This oxygen-rich blood is then received by the left atrium. It passes the blood to the left ventricle which then pumps it out to the rest of the body to supply oxygen to all the cells.
What happens in atrial fibrillation?
The heart’s contraction is triggered by electrical impuleses which are generated by the sinoatrial (SA) node in the heart wall. It is also known as the sinus node or the natural pacemaker of the heart. The impulses pass through the atria which causes the atria to contract. Then the impulses travel through the atrioventricular (AV) node which causes the ventricles to contract.
Normally these impulses occur at regular intervals. This ensures that the atria first contract and thereafter the ventricles contract. However, in atrial fibrillation there is an abnormality in the way these impulses are triggered and conducted. As a result it cause abnormally rapid and irregular contractions of the heart with quivering/fluttering of the atria. The ventricles may also be affected.
Read more on irregular heart rhythm.
What causes atrial fibrillation?
The cause of the abnormalities that lead to atrial fibrillation may include:
- Congenital heart disease (defects present from birth)
- Coronary artery disease
- Heart attack
- Heart valve disease
- Hypertension (high blood pressure)
- Hyperthyroidism (overactive thyroid gland)
- Lung diseases
- Severe illnesses (stress)
- Sick sinus syndrome (a type of heart problem)
- Sleep apnea
- Stimulants, including certain medication, illicit drugs, caffeine, tobacco or alcohol
- Surgery to the heart
- Viral infections
Apart from the conditions mentioned above, some people are at a greater risk of atrial fibrillations. These risk factors may include:
- Advancing age
- Alcohol consumption, especially binge drinking
- Family history of atrial fibrillation
- Tobacco smoking
When atrial fibrillation occurs without any damage to the heart or diseases that can affect heart function, then it is known as long atrial fibrillation.
Signs and Symptoms
There are various signs and symptoms that may arise with atrial fibrillation. Apart from the irregularity in heart rhythm and rate, blood oxygenation and circulation may be compromised. This can give rise to other signs and symptoms away from the heart since the entire body is dependent on sufficient oxygen and blood to function properly.
- Fatigue with reduced ability to undertake physical activity.
- Palpitations which is a pounding, racing or fluttering sensation in the chest. There may also be chest pain.
- Weakness throughout the body.
- Lightheadedness and dizziness.
- Rapid heart rate (tachycardia).
- Shortness of breath and sometimes even difficulty breathing.
- Difficulty concentrating or confusion.
- Fainting (loss of consciousness) in more severe cases.
When complications like a stroke or heart failure arise then there may be other signs and symptoms. This can include tingling or numbness usually on one side of the body, weakness or paralysis, disturbances of senses like blurred vision and swelling of the legs among other symptoms.
How long does atrial fibrillation last?
Atrial fibrillation is not always continuous. It can arise and resolve within minutes to hours or it may persist for long periods of time, months and even years, without resolving. Therefore atrial fibrillation may be classified as:
- Occasional (paroxysmal): Lasts for minutes to hours. Resolves on its own.
- Persistent: Irregularity continues until treatment restores it to normal.
- Long-standing persistent: Continous unless treated and lasts longer than 12 months.
- Permanent: Continous and heart rhythm cannot be restored.
Although there is a greater risk of complications with persistent atrial fibrillation, sometimes even short term atrial fibrillation can be serious if the abnormality of the heart beat is severe.
Treatment of Atrial Fibrillation
Diagnostic investigations like an electrocardiogram (ECG) are required to confirm the presence of atrial fibrillation. The aim of treatment is to restore the heart rhythm to normal. This is known as cardioversion and may include:
- Medication known as anti-arrhythmic drugs.
- Electrical shock to allow the SA node to ‘reset’.
In addition, treatment to prevent complications may also be prescribed. Blood-thinning agents prevent the formation of blood clots that can arise with with disturbance in blood flow due to the quivering or fluttering of the heart.
Sometimes surgery is required to treat atrial fibrillation. Surgical procedures are conducted to:
- Destroying cells that trigger electrical impulses (catheter ablation).
- Interrupting electrical signals from the SA node traveling to the AV node (atrioventricular ablation). A pacemaker may then be required.
- Stimulating scar tissue formation in certain areas of the heart wall so that electrical impulses can be impaired from traveling (surgical maze procedure).